Method for manufacturing rotator with bearing

ABSTRACT

A pulley includes a radial rolling bearing and a pulley main body which are integrated to each other by an insert molding method. Therefore, a metal insert member is not required between the resin pulley main body and the radial rolling bearing, thereby reducing production cost of the pulley. Further, an axial dimension of an outer ring of the radial rolling bearing is set larger than an axial dimension of an inner ring thereof, so that a contact area between the radial rolling bearing and the pulley main body is increased. Therefore, a connection strength between the radial rolling bearing and the pulley main body is increased, and a surface area of the radial rolling bearing is increased, thereby improving heat radiation performance of the radial rolling bearing.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to and claims priority from Japanese Pat.Application No. 2002-5839 filed on Jan. 15, 2002, the content of whichis hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotator including a bearing, which issuitably used for a pulley for transmitting power. Further, the presentinvention relates to a method for manufacturing the rotator.

2. Description of Related Art

In a conventional pulley for transmitting motive power disclosed inJP-A-2001-227620, a generally cylindrical metal member is integratedwith a resinous pulley main body by using an insert molding method.However, since a bearing is press-fitted to an inner peripheral surfaceof the metal member, the inner peripheral surface requires finishing.operation such as cutting. Therefore, it is difficult to reduce thenumber of working steps of the pulley and the number of componentsthereof.

SUMMARY OF THE INVENTION

In view of the above problem, it is an object of the present inventionto reduce production cost of a rotator such as a pulley.

It is an another object of the present invention to provide a rotatorthat is manufactured in low cost, while a bonding strength between arotating member and a bearing is increased.

According to the present invention, a rotator includes a rotating membermade of resin, and a bearing attached to a radial inner side of therotating member. The bearing includes an outer ring integrated to therotating member by an insert molding, an inner ring positioned at aradial inside of the outer ring, and a bearing ball that is disposed torolling-contact an inner peripheral surface of the outer ring and anouter peripheral surface of the inner ring. In the rotator, the outerring has an axial dimension larger than an axial dimension of the innerring in an axial direction of the rotating member. Because the bearingand the rotating member are integrated to each other through the insertmolding, a metal insert member is not required to be disposed betweenthe rotating member and the bearing, thereby reducing production cost ofthe rotator. In addition, because the outer ring has the axial dimensionlarger than the axial dimension of the inner ring, a bonding areabetween the bearing and the rotating member can be increased, and aconnection strength therebetween can be increased while an outer surfaceof the bearing can be increased. Accordingly, heat radiation performanceof the bearing can be improved.

Preferably, the outer ring has an outer peripheral surface contactingthe rotating member, and the outer peripheral surface has an unevenportion. Therefore, the outer ring of the bearing can be engaged withthe rotating member in the insert molding, and the connection strengthbetween the bearing and the rotating member can be effectivelyincreased.

Preferably, the rotating member includes two projections protruding to aradial inside of the outer peripheral surface of the outer ring, and thetwo projections contact two axial ends of the outer ring to pinch theouter ring from the two axial ends. Therefore, the bearing is fixed bythe projections of the rotating member in the axial direction, andconnection strength between the bearing and the rotating member can befurther improved. On the other hand, the outer ring has the outerperipheral surface, two axial ends and two chamfer surfaces connectingthe outer peripheral surface and the axial ends. In this case, therotating member contacts the outer peripheral surface and the chamfersurfaces of the outer ring.

Further, the outer ring of the bearing includes a heat radiation portionexposed to atmospheric air, from which heat is radiated to atmosphericair. The heat radiation portion has a heat-radiation facilitatingportion for facilitating heat radiation, and the heat-radiationfacilitating portion is provided to increase a heat radiation area ofthe heat radiation portion. For example, the heat-radiation facilitatingportion is a plurality of recesses provided on an inner peripheralsurface of the heat radiation portion. Alternatively, the heat-radiationfacilitating portion is a fin press-fitted to an inner peripheralsurface of the heat radiation portion, or an uneven portion provided onan axial end of the heat radiation portion.

The rotator of the present invention is manufactured by the insertmolding. In the inserting molding, at least the outer ring of thebearing is arranged in a die at a predetermined position, and a resin isinjected in the die to form the rotating member integrated to the outerring, at a radial outside of the outer ring. When only the outer ring ofthe bearing is provided in the die in the insert molding, the bearingball is attached to the outer ring so that the bearing ballrolling-contacts the inner peripheral surface of the outer ring, and theinner ring is attached to the bearing ball at a radial inside of theouter ring so that the bearing ball rolling-contacts the inner ring.Alternatively, all the bearing including the outer and inner rings andthe bearing ball can be arranged in the die in the insert molding.Accordingly, the bearing and the rotating member can be readilyintegrated.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and advantages of the present invention will be morereadily apparent from the following detailed description of pluralembodiments when taken together with the accompanying drawings, inwhich:

FIG. 1A is a sectional view showing a pulley according to a firstembodiment of the present invention, and FIG. 1B is a side view takenfrom the arrow IB in FIG. 1A;

FIG. 2 is a cross-sectional view showing a pulley main body and a radialrolling bearing integrated with the pulley main body, according to thefirst embodiment;

FIG. 3 is a side view taken from the arrow III in FIG. 2;

FIG. 4 is a side view taken from the arrow IV in FIG. 2;

FIG. 5 is an enlarged view showing the V portion in FIG. 2;

FIG. 6A is a side view showing the radial rolling bearing according tothe first embodiment, and FIG. 6B is a cross-sectional view showing theradial rolling bearing according to the first embodiment;

FIG. 7 is an enlarged view showing a portion corresponding to the Vportion in FIG. 2 in an insert molding, according to the firstembodiment;

FIG. 8A is a side view showing a radial rolling bearing according to asecond embodiment of the present invention, and FIG. 8B is across-sectional view showing the radial rolling bearing according to thesecond embodiment;

FIG. 9 is a cross-sectional view showing a radial rolling bearingaccording to a third embodiment of the present invention;

FIG. 10 is a cross-sectional view showing a radial rolling bearingaccording to a fourth embodiment of the present invention; and

FIG. 11 is a cross-sectional view showing a radial rolling bearingaccording to a fifth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be describedhereinafter with reference to the appended drawings.

(First Embodiment)

In the first embodiment, a rotator of the present invention is typicallyused for a pulley for transmitting motive power of a vehicle engine to acompressor. As shown in FIGS. 1A, 1B and 2, a pulley 1 includes a pulleymain body 2 that is a rotating member made of resin, and a radialrolling bearing 3. Plural rows of V-grooves 2 a are formed on an outerperipheral portion of the pulley main body 2, and a pulley drive belt isprovided on the plural rows of V-grooves 2 a. The radial rolling bearing3 is attached to a radial inner side of the pulley main body 2. FIG. 3is a side view when being viewed from the arrow III in FIG. 2, and FIG.4 is a side view when being viewed from the arrow VI in FIG. 2. Further,FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 3.

As shown in FIG. 5, the radial rolling bearing 3 includes an outer ring3 a integrated to the pulley main body 2, bearing balls 3 b, an innerring 3 c disposed radial inside of the outer ring 3 a, a retainer 3 dfor holding the bearing balls 3 b, grease contained in a clearance 3 ebetween the outer and inner rings 3 a, 3 c, a seal member 3 f forpreventing the grease from flowing out from the clearance 3 e and thelike. The bearing balls 3 b rolling-contact an inner peripheral surfaceof the outer ring 3 a, and an outer peripheral surface of the inner ring3 c. The outer ring 3 a, the inner ring 3 c and the bearing balls 3 bare made of metal such as steel. The retainer 3 d is formed from resinsuch as nylon 66. The seal member 3 f is formed from resin such asacrylic rubber, and is reinforced by a metal core 3 g immersed in theseal member 3 f.

An axial dimension Lo of the outer ring 3 a is set larger than an axialdimension Li of the inner ring 3 c, so that the outer ring 3 a extendstoward a compressor 10. Further, a wall thickness To of the outer ring 3a is made larger than a wall thickness Ti of the inner ring 3 c. Here,the wall thickness To is a minimum wall thickness of the outer ring 3 a,that is, a wall thickness of the outer ring 3 a at the positions wherethe bearing ball 3 b contacts the outer ring 3 a. Further, the wallthickness Ti is a minimum wall thickness of the inner ring 3 c, that is,a wall thickness of the inner ring 3 c at the positions where thebearing ball 3 b contacts the inner ring 3 c. As shown in FIGS. 6A, 6B,a spiral recess portion 3 h (uneven portion) having plural recesses andprotrusions is formed on an outer peripheral surface of the outer ring 3a at the position where the pulley main body 2 contacts the outer ring 3a. As shown in FIG. 1, a front housing of the compressor 10 ispress-fitted to the inner peripheral surface of the inner ring 3 c. Asshown in FIG. 7, the outer ring 3 a is provided with an outer peripheralsurface 3 k, an end surface 3 j and a chamfer curved surface 3 mconnecting the outer peripheral surface 3 k and the end surface 3 j. Asshown in FIG. 5, the pulley main body 2 includes projection portions 2 ceach having an approximate triangular cross-section. The projectionportions 2 c of the pulley main body 2 contact the chamfer curvedsurfaces 3 m so as to pinch the outer ring 3 a from both the axial ends.

In FIGS. 1A and 1B, a center hub 4 is for transmitting torquetransmitted to the pulley main body 2, to a shaft 11 of the compressor.The center hub 4 is connected to the pulley main body 2 to be engagedwith each other through a damper that is made of an elastic member suchas rubber. The center hub 4 includes a cylindrical portion 4 a having afemale screw portion, an annular portion 4 c provided with a projectionportion 4 b, and a bridge portion 4 d and the like. A male screwportion, formed on an outer peripheral surface of the shaft 11 of thecompressor 10, is screw connected to the female screw portion of thecylindrical portion 4 a. The projection portion 4 b is engaged with awall-like projection 2 b of the pulley main body 2, shown in FIG. 3,through the damper. The bridge portion 4 d mechanically connects theannular portion 4 c and the cylindrical portion 4 a, so that torque fromthe annular portion 4 c is transmitted to the cylindrical portion 4 athrough the bridge portion 4 d. Further, the strength of the bridgeportion 4 d is set so that the bridge portion 4 d fractures when thetransmitted torque is larger than a predetermined torque. Here, thebridge portion 4 d and the cylindrical portion 4 a are integrally formedby sintering of metal powder. Further, the bridge portion 4 d isintegrated with the annular portion 4 c by an insert molding methodwhile the annular portion 4 c and the projection portion 4 b are molded.

Next, a production method of the pulley 1 will be described withreference to FIG. 7. A melted resin is injected into a die space(cavity) defined by molding dice 21-23 after the radial rolling bearing3 is disposed at a predetermined position in the die space. At thistime, a space 24 is defined between the chamfer curved surfaces 3 m andthe molding dice 21-23 while the radial rolling bearing 3 is held at thepredetermined position by the contact between the molding dice 21, 22and the end surfaces 3 j of the outer ring 3 a. Therefore, theprojection portions 2 c, contacting the chamfer curved surfaces 3 mdisposed at both the axial ends of the outer ring 3 a, are integrated tothe pulley main body 2 in the insert molding.

According to the first embodiment, since the radial rolling bearing 3and the pulley main body 2 are integrated with each other by the insertmolding method, it is unnecessary to provide an insert metal memberbetween the resin pulley main body 2 and the radial rolling bearing 3,thereby reducing production cost of the pulley 1. Further, the axialdimension Lo of the outer ring 3 a is made larger than the axialdimension Li of the inner ring 3 c. Therefore, connection strength(bonding strength) between the radial rolling bearing 3 and the pulleymain body 2 can be increased by increasing a contact area therebetween,and a heat radiation can be increased by increasing a surface area ofthe radial rolling bearing 3. As shown in FIG. 6B, a heat radiationportion 3 p is a portion of the outer ring 3 a, exposed to atmosphericair.

The spiral recess portion 3 h is provided on the outer peripheralsurface of the outer ring 3 a at the contact portion contacting thepulley main body 2. Therefore, the radial rolling bearing 3 and thepulley main body 2 can be connected and engaged to each other in theinsert molding, thereby sufficiently increasing the connection strengththerebetween. Further, the wall thickness To of the outer ring 3 a ismade larger than the wall thickness Ti of the inner ring 3 c. Therefore,it can prevent a bearing-ball track surface of the outer ring 3 a frombeing deformed due to molding pressure in the insert molding, and anamount of heat capable of being transmitted to the heat radiationportion 3 p can be increased, thereby improving heat radiationperformance of the radial rolling bearing 3.

Since the radial rolling bearing 3 is pinched at both the axial endsthereof by the projection portions 2 c, the radial rolling bearing 3 isprevented from moving in the axial direction. Therefore, the radialrolling bearing 3 and the pulley main body 2 can be accurately connectedto each other. The projection portions 2 c are formed by using thechamfer curved surfaces 3 m provided at the axial ends of the outer ring3 a, at the time while the pulley main body 2 is molded. Therefore, theprojection portions 2 c can be formed without adding a particularprocess. Here, chamfer flat surfaces may be provided in the radialrolling bearing, in place of the chamfer curved surfaces 3 m. That is,the shape of the chamfer curved surface 3 m can be changed.

(Second Embodiment)

In the second embodiment, as shown in FIGS. 8A, 8B, an outer radialdimension D1 of the outer ring 3 a is defined at the position where thebearing balls 3 b are disposed, and an outer radial dimension D2 of theouter ring 3 a is defined at the other positions. The outer radialdimension D1 is made larger than the outer radial dimension D2, to formsteps on the outer ring 3 a as shown in FIGS. 8A and 8B. Therefore, themechanical strength of the outer ring 3 a can be increased, so that thebearing-ball track surface of the outer ring 3 a can be prevented frombeing deformed due to molding pressure in the insert molding. Further,an amount of heat capable of being transmitted to the heat radiationportion 3 p can be increased, thereby further improving heat radiationperformance of the radial rolling bearing 3. In the second embodiment,the other parts are similar to those of the above-described firstembodiment, and detail explanation thereof is omitted.

(Third Embodiment)

In the third embodiment, as shown in FIG. 9, a spiral recess portion 3 qis provided on an inner peripheral surface of the heat radiation portion3 p for facilitating the heat radiation. Therefore, the heat radiationarea of the heat radiation portion 3 p, that. is, the surface areathereof is increased. Here, the recess portion 3 q can be provided inanother shape such as a plural-concentric shape and a crossing-spiralshape, without being limited to the spiral shape. According to the thirdembodiment, by providing the recess portion 3 q in the heat radiationportion 3 p, the heat radiation can be effectively facilitated.

In the third embodiment, the other parts are similar to those of theabove-described first embodiment, and detail explanation thereof isomitted.

(Fourth Embodiment)

In the fourth embodiment, as shown in FIG. 10, the heat radiation areaof the heat radiation portion 3 p is increased by press-fitting a heatradiation fin 3 r to the inner surface of the heat radiation portion 3p, so that the heat radiation can be facilitated. The heat radiation fin3 r has an approximate U-shaped cross-section, and is made of aluminum.The heat radiation fin 3 r can be made of another metal such as copperwithout being limited to aluminum, and the cross-sectional shape of theheat radiation fin 3 r can be changed to the other shape such as a Lshape.

Accordingly, in the fourth embodiment, the heat radiation of the heatradiation portion 3 p can be effectively increased. In the fourthembodiment, the other parts are similar to those of the above-describedfirst embodiment, and detail explanation thereof is omitted.

(Fifth Embodiment)

In the fifth embodiment, as shown in FIG. 11, the heat radiation area ofthe heat radiation portion 3 p is increased by providing uneven portions3 s on the end surfaces 3 j of the heat radiation portion 3 p, so thatthe heat radiation of the heat radiation portion 3 p can be facilitated.For example, the uneven portions 3 s are recess portion recessed fromthe end surfaces 3 j. Accordingly, heat radiation of the heat radiationportion 3 p can be facilitated. In the fifth embodiment, the other partsare similar to those of the above-described first embodiment, and detailexplanation thereof is omitted.

Although the present invention has been fully described in connectionwith the above-described embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications will become apparent to those skilled in the art.

For example, in the above-described embodiments, the bearing includingthe outer and inner rings 3 a, 3 c is adopted as the radial rollingbearing 3. However, a shell type bearing eliminating the inner ring 3 cmay be adopted without being limited to the bearing 3 in the aboveembodiments. In the above-described embodiments, all the radial rollingbearing 3 is integrated to the pulley main body 2 by the insert moldingmethod. However, after the outer ring 3 a is integrated to the pulleymain body 2 by the insert molding method, the bearing balls 3 b and theinner ring 3 c can be attached to the outer ring 3 a integrated to thepulley main body 2.

Further, the present invention is not limited to the pulley as in theabove embodiments, but can be applied to the other rotating member.

Such changes and modifications are to be understood as being within thescope of the present invention as defined by the appended claims.

1-11. (Cancelled)
 12. A method for manufacturing a rotator, comprising:arranging an outer ring of a bearing in a die at a predeterminedposition; injecting a resin in the die to form a rotating memberintegrated to the outer ring, at a radial outside of the outer ring; andattaching a bearing ball to the outer ring so that the bearing ballrolling-contacts an inner peripheral surface of the outer ring; andattaching an inner ring to the bearing ball at a radial inside of theouter ring so that the bearing ball rolling-contacts the inner ring,wherein an axial dimension of the outer ring is made larger than anaxial dimension of the inner ring.
 13. The method according to claim 12,further comprising forming an uneven portion on an outer peripheralsurface of the outer ring before the injecting.
 14. The method accordingto claim 12, wherein the outer ring and the inner ring are formed suchthat a wall thickness of the outer ring is larger than a wall thicknessof the inner ring, in contacting portions of the outer ring and theinner ring, contacting the bearing ball.
 15. A method for manufacturinga rotator, comprising: arranging at least an outer ring of a bearing ina die at a predetermined position, the outer ring having an outerperipheral surface, two axial ends contacting the die, and two chamfersurfaces connecting the outer peripheral surfaces and the axial ends;injecting a resin in the die to form a rotating member integrated to theouter ring at a radial outside of the outer ring, wherein twoprojections of the rotating member, contacting the two chamfer surfaces,are formed in the injecting due to the two chamfer surfaces.
 16. Themethod according to claim 15, wherein the bearing is formed such that abearing ball rolling-contacts the outer ring and an inner ring.
 17. Themethod according to claim 15, wherein all the bearing is placed in thedie in the arranging.